Reading device, image forming apparatus, correction value calculating method, and storage medium storing program code

ABSTRACT

A reading device including a position reference member having a reference pattern having a line extending along a first direction of the position reference member, the position reference member movable in a second direction orthogonal to the first direction; a reader including a plurality of sensor chips arranged along the first direction, each of the sensor chips having a length defined by a plurality of pixels; and circuitry. The circuitry is configured to detect the reference pattern of the position reference member using the reader; determine coordinates of at least two sensor chips in the second direction, based on the detected reference pattern of the position reference member; and correct a position of a reading target in the second direction based on the coordinates determined for the at least two sensor chips of the reader in the second direction.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is based on and claims priority pursuant to 35U.S.C. § 119(a) to Japanese Patent Application No. 2017-231296, filed onNov. 30, 2017 and Japanese Patent Application No. 2018-137931, filed onJul. 23, 2018, in the Japan Patent Office, the entire disclosures ofwhich are hereby incorporated by reference herein.

BACKGROUND Technical Field

Embodiments of the present disclosure relates to a reading device, animage forming apparatus incorporating the reading device, a correctionvalue calculating method, and a storage medium storing program code forcausing a computer to execute the method.

Background Art

The technology has been known that reads the outer edge position and theprocessing position of a conveyed object using a reader such as acontact image sensor (CIS) mounted in a reading device so as to correcta position to which the conveyed object has been conveyed and theprocessing position of the conveyed object.

Further, the technology is also known that detects displacement of theinstallation position of the reader by reading a proof sheet.

SUMMARY

In one aspect of this disclosure, there is provided an improved readingdevice including a position reference member having a reference patternhaving a line extending along a first direction of the positionreference member, the position reference member movable in a seconddirection orthogonal to the first direction; a reader including aplurality of sensor chips arranged along the first direction, each ofthe sensor chips having a length defined by a plurality of pixels; andcircuitry. The circuitry is configured to detect the reference patternof the position reference member using the reader; determine coordinatesof at least two sensor chips in the second direction, based on thedetected reference pattern of the position reference member; and correcta position of a reading target in the second direction based on thecoordinates determined for the at least two sensor chips of the readerin the second direction.

In another aspect of this disclosure, there is provided an improvedmethod of calculating a correction value using a position referencemember including a reference pattern having a line extending along afirst direction of the position reference member, the position referencemember movable in a second direction orthogonal to the first direction,and a reader including a plurality of sensor chips arranged along onedirection of the reader. The method includes detecting, using thereader, the reference pattern having the line extending along the firstdirection of the reference pattern member, the reference patterncorresponding to each of the plurality of sensor chips arranged alongthe one direction in the reader, and each of the sensor chips having alength defined by a plurality of pixels; determining coordinates of atleast two sensor chips in the second direction, among the plurality ofsensor chips, based on the detected reference pattern of the positionreference member; and correcting a position of a reading target in thesecond direction based on the coordinates determined for the at leasttwo sensor chips of the reader in the second direction.

In still another aspect of this disclosure, there is provided animproved image forming apparatus including the reading device; a printengine; and circuitry. The circuitry is configured to control aconveyance of a recording medium onto which an image is formed by theprint engine; detect an outer shape of the recording medium and aposition of an image pattern on the recording medium by reading theimage formed on the recording medium using the reading device; andcorrect a position of a reading target in the second direction based onthe coordinates determined for the at least two sensor chips of thereader in the second direction.

In yet another aspect of this disclosure, there is provided an improvednon-transitory recording medium storing a program for causing a computerto execute the above-described method.

BRIEF DESCRIPTION OF THE DRAWINGS

The aforementioned and other aspects, features, and advantages of thepresent disclosure will be better understood by reference to thefollowing detailed description when considered in connection with theaccompanying drawings, wherein:

FIG. 1 is a schematic illustration of a hardware configuration of aprinting system according to an embodiment of the present disclosure;

FIG. 2 is an illustration of a reader and the position reference memberof a reading device according to an embodiment of the presentdisclosure;

FIG. 3 is an illustration of the relative positions of the reader andthe position reference member in FIG. 2;

FIG. 4 is an illustration for explaining difficulties in applying a CISto the reader;

FIG. 5 is an illustration of an example of the reference line arrangedon the position reference member according to an embodiment of thepresent disclosure;

FIG. 6 is an illustration of the relative positions of the positionreference member and the reader according to an embodiment of thepresent disclosure;

FIG. 7 is a block diagram of a hardware configuration of the printingsystem in FIG. 1, describing an example of electric connection ofhardware elements;

FIG. 8 is a block diagram of a functional configuration of the printingsystem in FIG. 1;

FIGS. 9A and 9B are illustrations of an example of how a coordinate inthe sub-scanning direction of each sensor chip of the reader in FIG. 3is calculated, according to an embodiment of the present disclosure;

FIG. 10 is an illustration of a method of correcting inclination of thereader according to an embodiment of the present disclosure;

FIG. 11 is an illustration of a method of correcting inclination of tworeaders according to an embodiment of the present disclosure;

FIGS. 12A, 12B, and 12C are illustrations of a method of calculating anouter shape of a recording medium and a position of an image pattern onthe recording medium according to an embodiment of the presentdisclosure;

FIGS. 13A and 13B are illustrations of examples of images detected bythe reader according to an embodiment of the present disclosure;

FIG. 14 is an illustration of a table of a correction example in FIG.13B; and

FIG. 15 is a flowchart of processes of correction processing.

The accompanying drawings are intended to depict embodiments of thepresent disclosure and should not be interpreted to limit the scopethereof. The accompanying drawings are not to be considered as drawn toscale unless explicitly noted.

DETAILED DESCRIPTION

In describing embodiments illustrated in the drawings, specificterminology is employed for the sake of clarity. However, the disclosureof this patent specification is not intended to be limited to thespecific terminology so selected and it is to be understood that eachspecific element includes all technical equivalents that have the samefunction, operate in a similar manner, and achieve similar results. Asused herein, the singular forms “a”, “an”, and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise.

Although the embodiments are described with technical limitations withreference to the attached drawings, such description is not intended tolimit the scope of the disclosure and all of the components or elementsdescribed in the embodiments of this disclosure are not necessarilyindispensable.

Embodiments of the present disclosure are described in detail withreference to the drawings. Like reference numerals designate identicalor corresponding components throughout the several views and adescription of same is omitted.

With initially reference with the figures, a description is providedbelow of embodiments of a reading device, an image forming apparatusincorporating the reading device, a correction value calculating method,and program. In the following, the cases where the reading device andthe image forming apparatus are applied to a printing system providedwith a printing device such as a commercial printing machine (productionprinting machine) that prints a large number of sheets continuously in ashort period of time are described. However, no limitation is intendedthereby.

FIG. 1 is a schematic illustration of a hardware configuration of aprinting system 1 according to an embodiment of the present disclosure.As illustrated in FIG. 1, the printing system 1 as an image formingapparatus includes a printing device 100, a medium position detector 200(an example of a position detector), and a stacker 300.

The printing device 100 includes an operation panel 101, tandem typeelectrophotographic image forming units 103Y, 103M, 103C, and 103K, atransfer belt 105, a secondary transfer roller 107, a sheet feeder 109,a pair of conveying rollers 102, a fixing roller 104, and a sheetreverse path 106.

The operation panel 101 is an operation display unit that enables a userto input various operations to the printing device 100 and the mediumposition detector 200 and displays various screens.

In the printing device 100, a toner image is formed on each of the imageforming units 103Y, 103M, 103C, and 103K by an image forming process (acharging process, an exposing process, a developing process, a transferprocess, and a cleaning process), and the formed toner image istransferred onto the transfer belt 105. In the present embodiment, ayellow toner image is formed on the image forming unit 103Y, a magentatoner image is formed on the image forming unit 103M, a cyan toner imageis formed on the image forming unit 103C, and a black toner image isformed on the image forming unit 103K. However, no limitation isintended thereby.

The transfer belt 105 conveys the toner image (full-color toner image)in which the toner images of the image forming units 103Y, 103M, 103C,and 103K are transferred to be superimposed on each other, to thesecondary transfer position of the secondary transfer roller 107. In thepresent embodiment, a yellow toner image is first transferred to thetransfer belt 105, and a magenta toner image, a cyan toner image, and ablack toner image are sequentially superimposed one atop another on thetransfer belt 105 while being transferred from the image forming units103Y, 103M, 103C, and 103K as the transfer belt 105 rotates. However, nolimitation is intended thereby.

The sheet feeder 109 accommodates a plurality of recording media to beprocessed (a conveyed objects) in a superposed manner, and feeds arecording medium. Examples of the recording medium include recordingpaper (transfer paper). However, the recording medium is not limited tothis, and examples of the recording medium may include media capable ofrecording images such as coated paper, thick paper, overhead projector(OHP) sheets, plastic films, and copper foil.

In the present embodiment, the recording medium on which an image is tobe formed is the object to be processed (conveyed object). However, nolimitation is indicated thereby. Alternatively, for example, a sheetthat is not a target on which an image is to be formed such as pregregmay be an object to be processed (conveyed object).

The pair of conveying rollers 102 conveys the recording medium fed bythe sheet feeder 109 in the direction of arrow s on the conveying patha.

The secondary transfer roller 107 collectively transfers the full-colortoner image conveyed by the transfer belt 105 onto the recording mediumconveyed by the pair of conveying rollers 102 at the secondary transferposition.

The fixing roller 104 fixes the full-color toner image on the recordingmedium by heating and pressurizing the recording medium onto which thefull-color toner image is transferred.

In the case of single-sided printing, the printing device 100 sendsprinted material that is the recording medium on which the full-colortoner image has been fixed, to the medium position detector 200. On theother hand, in the case of duplex printing, the printing device 100sends the recording medium on which the full-color toner image has beenfixed, to the sheet reverse path 106.

The sheet reverse path 106 reverses the front and back surfaces of therecording medium by switching back the fed recording medium, and conveysthe recording medium in the direction of the arrow t. The recordingmedium conveyed through the reversing path 106 is conveyed again by thepair of conveying rollers 102, and a full-color toner image istransferred to the surface of the recording medium opposite to thepreviously transferred surface by the secondary transfer roller 107. Thetransferred full-color toner image is fixed to the surface by the fixingroller 104, and the recording medium is sent as printing material to themedium position detector 200 and to the stacker 300.

The medium position detector 200 located downstream of the printingdevice 100 includes a reader 201 and a position reference member 202.

The reader 201 is implemented by, for example, a CIS in which aplurality of image sensors such as complementary metal oxidesemiconductors (CMOS's) are arranged in line. The reader 201 receiveslight reflected by a reading target and outputs an image signal.Specifically, the reader 201 reads the position (conveyance position) towhich the recording medium is conveyed from the printing device 100 andthe processing position (printing position) of the recording medium.Further, the reader 201 reads the position reference member 202 as anobject to be read.

The CIS used in the reader 201 is typically configured to include aplurality of sensor chips 210 (see FIG. 4) along the main scanning, eachof the sensor chips 210 including a plurality of pixels. Thus, the CIShas an effective reading length in the main scanning direction.

The position reference member 202 is a reference plate for correcting aninstallation position of each sensor chip 210 of the reader 201including the plurality of sensor chips 210. By correcting theinstallation position of each sensor chip 210 of the reader 201 usingthe position reference member 202 as described above, the position ofthe image can be detected at higher accuracy.

Then, the medium position detector 200 discharges the recording mediumread by the reader 201, to the stacker 300.

The stacker 300 includes, for example, a tray 301. The stacker 300stacks the recording medium discharged by the medium position detector200, onto the tray 301.

Next, a description is given below of the reader 201 and the positionreference member 202 in the medium position detector 200.

The method, in which the outer edge position and the processing positionof a conveyed object are read by the reader such as the CIS so as tocorrect the conveyance position and processing position of the conveyedobject, might result in deterioration in accuracy.

FIG. 2 is an illustration of the reader 201 and the position referencemember 202 according to an embodiment of the present disclosure. Asillustrated in FIG. 2, the position reference member 202 is provided ona rotator 203 that is rotationally driven by a motor 204.

That is, the position reference member 202 is moved by the rotator 203that is rotated at a constant speed by the motor 204. The positionreference member 202 moves to face the reader 201 at a predeterminedtiming as the rotator 203 rotates.

The position reference member 202 is rotated at a constant speed alongthe sub-scanning direction as described above so that the reader 201 canread a reference line X (see FIG. 4) as a reference pattern including aline extending in a predetermined direction on the position referencemember 202. As a result, the inclination of the position referencemember 202 in the sub-scanning direction can be detected.

In FIG. 2, the position reference member 202 is attached to the rotator203 and the position reference member 202 is moved at a constant speedin the sub-scanning direction. However, no limitation is intendedthereby. For example, the position reference member 202 may be disposedto linearly move.

In FIG. 2, the position reference member 202 is configured to move at aconstant speed in the sub-scanning direction. Alternatively, the reader201 may be moved at a constant speed in the sub-scanning directioninstead.

FIG. 3 is an illustration of the relative positions of the reader 201and the position reference member 202.

As illustrated in FIG. 3, the position reference member 202 has areference position (support point) that corresponds to the position of aleading pixel of the image sensor at one end (leading end) of the reader201 in the main scanning direction.

Further, the reader 201 also has a reference position (support point)that corresponds to a position of the leading pixel corresponding to thereference position of the position reference member 202.

The following describes issues when the CIS is applied to the reader201.

FIG. 4 is an illustration for explaining issues in applying a CIS to thereader 201.

As illustrated in FIG. 4, for example, when the reader 201 is attachedobliquely to the position reference member 202, the position of theposition reference member 202 is detected less accurately even if thereader 201 receives light reflected by the reading target and reads animage corresponding to the received light. Thus, the accuracy of theposition detection of the position reference member 202 reduces and aproper correction operation fails (variation in installation positions).

In addition, when the CIS is applied to the reader 201 as illustrated inFIG. 4, the pixels are arranged uniformly and linearly in each sensorchip 210, but the positions of the plurality of sensor chips 210 in thesub-scanning direction may not be aligned on the same line (variation inchip positions in the sub-scanning direction).

In view of such circumstances, the following configurations are proposedto improve the accuracy of detection of the positions.

FIG. 5 is an illustration of an example of a reference line X arrangedon the position reference member 202.

As illustrated in FIG. 5, a reference line X having a given length isarranged on the position reference member 202. The reference line Xarranged on the position reference member 202 includes, for example, afirst line X1 (horizontal line X1) parallel with the main scanningdirection (a predetermined direction) of the reader 201 and a secondline X2 (vertical line) extending in a direction orthogonal to the mainscanning direction.

As illustrated in FIG. 5, the vertical line X2 of the reference line Xis arranged at a position corresponding to the center of each sensorchip 210 on the substrate of the reader 201.

Further, the vertical lines X2 of the reference line X are arranged atequal interval on the position reference member 202 to correspond to therespective sensor chips 210 on the substrate of the reader 201. Thus,each sensor chip 210 can read the vertical line X2.

The vertical line X2 is used to correct the position of the sensor chip210 in the main scanning direction. In addition, the inclination of thesensor chip 210 may be corrected more accurately by correcting theposition in the main scanning direction of the sensor chip 210 with thevertical line X2.

In addition, each horizontal line of the reference line X is arrangedbetween the vertical lines over the plurality of sensor chips 210 on thesubstrate of the reader 201.

As illustrated in FIG. 5, a gap is formed between the vertical line andthe horizontal line on the position reference member 202. With such aconfiguration, even if the horizontal line falls within the readingrange of the reader 201, the coordinate of the vertical line can becalculated.

However, the reference line X is not limited to such a configuration andmay have a configuration in which the vertical line X2 and thehorizontal line X1 are in contact with each other.

Ideally, a horizontal line detection unit 112 (FIG. 8) reads thehorizontal line X1 for each sensor chip 210 of the reader 201 to detecta coordinate of each sensor chip 210 in the sub-scanning direction, andreads two horizontal lines X1 corresponding to the sensor chips 210 atboth ends of the reader 201 to detect the inclination of the reader 201,so as to correct the reading result of the reader 201. However, such aconfiguration exhibits the following disadvantageous effects:

1) the processing to be performed becomes complicated and takes moretime because a position in the sub-scanning direction is to be detectedfor each pixel;

2) the correction values of all the pixels are obtained and recorded ina memory, which requires a memory capacity sufficient to store all thepixel correction values; and

3) information is extracted from a table having a greater number of datawhen using the correction value so that the processing to be performedbecomes complicated and takes more time.

In view of such circumstances, in at least one embodiment of the presentdisclosure, the horizontal line detection unit 112 reads two horizontallines X1 corresponding to the sensor chips 210 at the both ends of thereader 201 so as to detect two coordinates in the sub-scanningdirection, thus obtaining inclination of the reader 201 from the twocoordinates in the sub-scanning direction.

Then, the inclination degree of each sensor chip 210 (each pixel) of thereader 201 is obtained from the total inclination of the reader 201obtained by reading the two horizontal lines X1 corresponding to thesensor chips 210 at the both ends of the reader 201. Thus, theprocessing load required for the operations of detecting positions inthe sub-scanning direction and recording the detection results can bereduced.

If the position reference member 202 expands and contracts due to anyeffect (e.g., the heat generation of the peripheral components), theposition reference member 202 fails to function as an absolutepositional reference. As a result, the accuracy of the detection of thepositions might deteriorate. To avoid such a situation, the positionreference member 202 according to the embodiments of the presentdisclosure is made of material whose linear expansion coefficient islower than that of the substrate of the reader 201 and whose amount ofexpansion and contraction due to the effect of ambient temperature isnegligibly small for detecting the position.

In the present embodiment, the position reference member 202 is made of,for example, glass in consideration of an assumed temperature variationrange and linear expansion coefficient related to the assumedtemperature variation range.

It should be noted that the material of the position reference member202 is not limited to such material, and it is preferable to use quartzglass or the like in order to detect the position of a medium at higheraccuracy when the temperature variation range of the reader 201 is wide.

FIG. 6 is an illustration for describing the relative positions of theposition reference member 202 and the reader 201. The reader 201 such asCIS typically has characteristics that image characteristics change withthe height (depth) direction.

Typical examples of such image characteristics include a modulationtransfer function (MTF) (depth of focus) and depth of illumination. Sometypes of readers 201 have characteristics that differ with the positionin the main scanning direction, in addition to the height (depth).

In view of such characteristics, in the present embodiment, the positionreference member 202 and the reader 201 are disposed such that the depth(height) directional position at which the reader 201 reads therecording medium matches the depth (height) at which the reader 201reads the reference line X on the position reference member 202.

With such a configuration, the effects of the changes in imagecharacteristics can be reduced, in particular minimized, and thus theaccuracy of the detection of the positions can be improved.

FIG. 7 is a block diagram of a hardware configuration of the printingsystem 1, describing an example of electric connection of hardwarecomponents.

As illustrated in FIG. 7, the printing system 1 includes a controller 10and engines 60 and 70, which are connected with each other via aperipheral component interface (PCI) bus.

The controller 10 controls entire operation of the printing system 1. Inan example operation, the controller 10 controls drawing, communication,or user inputs to an operation panel 101 as an operation display unit.The engine 60 is an engine connectable to the PCI bus 919. Examples ofthe engine 60 includes a scanner engine such as the reader 201.

The engine 60 includes, in addition to the engine part, an imageprocessing part such as error diffusion or gamma conversion. The engine70 is an engine connectable to the PCI bus 919. Examples of the engine70 includes a print engine such as a plotter including the image formingunits 103Y, 103M, 103C, and 103K.

The controller 10 includes a central processing unit (CPU) 11, a northbridge (NB) 13, a system memory (MEM-P) 12, a south bridge (SB) 14, alocal memory (MEM-C) 17, an Application Specific Integrated Circuit(ASIC) 16, and a hard disc drive (HDD) 18. The NB 13 and the ASIC 16 areconnected through an Accelerated Graphics Port (AGP) bus 15. Further,the MEM-P 12 includes a read only memory (ROM) 12 a and a random accessmemory (RAM) 12 b.

The CPU 11 controls entire operation of the printing system 1. The CPU11 is connected to another device via a chip set constituted by the NB13, the MEM-P 12, and the SB 14.

The NB 13 is a bridge for connecting the CPU 11, the MEM-P 12, the SB14, and the AGP bus 15 to one other. The NB 13 includes a memorycontroller to control reading and writing data to and from the MEM-P 12,a PCI master, and an AGP target.

The MEM-P 12 is a system memory used as, for example, a memory to storeprograms or data, a memory to deploy programs or data, and a memory tostore drawing data for printing. The MEM-P 12 includes the ROM 12 a andthe RAM 12 b.

The ROM 12 a is a read only memory used as a memory to store programs ordata. The RAM 12 b is a read-write memory used as, for example, a memoryto deploy programs or data and a memory to store drawing data forprinting.

The SB 14 connects the NB 903 with a PCI device or a peripheral device.The SB 14 is connected to the NB 12 via the PCI bus. The networkinterface (I/F) and the like are also connected to the PCI bus.

The ASIC 16 is an integrated circuit (IC) dedicated to an imageprocessing that includes image processing hardware elements. The ASIC916 functions as a bridge that connects the AGP bus 15, PCI bus, HDD 18,and MEM-C 17.

The ASIC 16 includes a peripheral component interconnect (PCI) target,an accelerated graphic port (AGP) master, an arbiter (ARB) as a core ofthe ASIC 16, a memory controller for controlling the MEM-C 17, aplurality of direct memory access controllers (DMACs) for rotating imagedata with a hardware logic, and a PCI unit for transferring data betweenthe engines 60 and 70 via the PCI bus.

The ASIC 16 is connected to a communication interface (I/F) 50, auniversal serial bus (USB) 40, an institute of electrical andelectronics engineers (IEEE) 1394 via the PCI bus. The operation panel101 is directly connected to the ASIC 16.

The MEM-C 17 is a local memory used as a buffer for image data to becopied or coded. The HDD 18 is a storage for storing image data,programs, font data, and forms.

The AGP bus 15 is a bus interface for a graphics accelerator card thatis proposed for enhancing the speed of graphic processing. The AGP bus15 directly accesses the MEM-P 12 with high throughput to enhance thespeed of the graphics accelerator card.

A program executed by the printing system 1 according to theabove-described embodiment may be stored in any desiredcomputer-readable storage medium such as a compact disc read-only memory(CD-ROM), a flexible disk (FD), a compact disc-recordable (CD-R), and adigital versatile disk (DVD) in an installable or executable fileformat, for distribution.

Further, the program executed by the printing system 1 according to theembodiments of the present disclosure may be stored on a computerconnected to a network such as the Internet and downloaded via thenetwork.

Alternatively, the program executed by the printing system 1 accordingto the embodiments of the present disclosure may be provided ordistributed via a network such as the Internet.

Next, a function that the CPU 11 of the printing system 1 performs byexecuting a program stored in the HDD 18 or the ROM 12 a will bedescribed. It should be noted that a description of known functions willbe omitted here, and the unique functions exerted by the printing system1 of the present embodiments will be described in detail.

FIG. 8 is a block diagram of a functional configuration of the printingsystem 1.

As illustrated in FIG. 8, the CPU 11 of the printing system 1 functionsas a reading control unit 110, a motor control unit 111, a horizontalline detection unit 112 as a reference pattern detection unit, adetection result storage unit 113, a calculation unit 114, and aposition detection unit 115.

In addition to the reading control unit 110, the motor control unit 111,the horizontal line detection unit 112, the detection result storageunit 113, the correction unit 114, and the position detection unit 115,the CPU 11 may further function as a conveyance control unit to controlconveyance of a recording medium.

In the present embodiment, the cases where the unique functions of theprinting system 1 are implemented by executing the program by the CPU 11are described above. Alternatively, some or all of the functions may beimplemented by hardware such as a dedicated circuit.

The motor control unit 111 outputs a drive signal to the motor 204 torotationally drive the rotator 203. In addition, the motor control unit111 outputs a drive stop signal to the motor 204 to stop the rotation ofthe rotator 203.

The reading control unit 110 outputs a reading start signal to thereader 201 to start reading.

Upon receiving the reading signal from the reading device 201, thereading control unit 110 outputs a reading end signal to the reader 201to terminate the reading operation.

The horizontal line detection unit 112 causes the motor control unit 111to move the position reference member 202 in the sub-scanning direction.Further, the horizontal line detection unit 112 causes the reader 201 toread the position reference member 202 moving in the sub-scanningdirection, under the control of the reading control unit 110. Then, thehorizontal line detection unit 112 detects the coordinate in thesub-scanning direction of each sensor chip 210 of the reader 201.

FIGS. 9A and 9B are illustrations for describing an example of how thecoordinate in the sub-scanning direction of each sensor chip 210 of thereader 201 is calculated.

As illustrated in FIG. 9A, the horizontal line detection unit 112 readshorizontal lines X1 of the position reference member 202 in regions An,An+1, . . . , An+m or regions Bn, Bn+1, Bn+m for the respective sensorchips 210 of the reader 201, to detect a coordinate of each sensor chip210 of the reader 201 in the sub-scanning direction.

As described above, the horizontal line X1 of the position referencemember 202 is read by each sensor chip 210 at the substantially samepixel position. Such a configuration is advantageous to calculation incorrection processing. However, no limitation is intended thereby.Alternatively, the horizontal line X1 of the position reference member202 can be read by each sensor chip 210 by changing the pixel positionfor each sensor chip 210.

More specifically, the horizontal line detection unit 112 reads a regionA or B (with a width of “m” number of pixel(s)) of each sensor chip 210of the reader 201 while rotating the position reference member 202 inthe sub-scanning direction. The read values of “m” number of pixels areaveraged for each line of each sensor chip 210 of the reader 201, andthe averaged value data is stored in the storage unit such as the RAM 12b and the HDD 18.

The horizontal line detection unit 112 detects the coordinate of eachsensor chip 210 of the reader 201 from the positions of the rising edgeand the falling edge of the obtained data.

The detection result storage unit 113 stores the coordinate of eachsensor chip 210 of the reader 201 detected by the horizontal linedetection unit 112, in the storage unit.

The correction unit 114 calculates a correction value of the inclinationof the reader 201 to correct the position in the sub-scanning directionto detect the position of the reading target. FIG. 10 is an illustrationof a method of correcting the inclination of the reader 201.

As illustrated in FIG. 10, the correction unit 114 calculates the totalinclination of the reader 201 from the coordinate in the sub-scanningdirection obtained by reading the horizontal lines X1 corresponding tothe sensor chips 210 at the both ends of the reader 201.

A description is given below of an example of calculation of the totalinclination of the reader 201 when twelve sensor chips 210 are arrangedin the reader 201 and each sensor chip 210 includes 216.5 pixels. Itshould be noted that 0.5 pixel corresponds to the distance set for thegap between the sensor chips 210.

The total inclination of the reader 201=(the coordinate of the twelfthsensor chip 210 (chip 12) in the sub-scanning direction—the coordinateof the first sensor chip 210 (chip 1) in the sub-scanningdirection)/(12×216.5). That is, the inclination of the reader 201 isobtained by subtracting the coordinate of the first sensor chip 210 inthe sub-scanning direction from the coordinate of the twelfth sensorchip 210 in the sub-scanning direction and dividing the subtracted valueby the product of 12 and 216.5.

After obtaining the inclination of the reader 201 as a whole, thecorrection unit 114 calculates a correction value in the sub-scanningdirection at the pixel used for detecting the position. Morespecifically, the correction unit 114 acquires one of the coordinates inthe sub-scanning direction of the sensor chips 210 of the reader 201,from the storage unit.

Then, using the acquired coordinate as a reference position, thecorrection unit 114 multiplies the total inclination of the reader 201and a specific pixel (target pixel) corresponding to the sensor chip210, to obtain a correction value of the target pixel.

An example of calculation of the correction value in the sub-scanningdirection is described below. It should be noted that the symbols “m”indicates the number of pixels in the sensor chip 210. That is, “m” canbe changed from 1 to 216 in this description.

Correction value=a positional coordinate of the n-th sensor chip 210(chip “n”) in the sub-scanning direction+total inclination of the reader201×“m” (Therefore, the correction value is obtained by adding theproduct of the total inclination of the reader 201 and “m” to thecoordinate of the n-th sensor) in the sub-scanning direction.

It should be noted that, when each sensor chip 210 has any desired pixelposition to read the horizontal line X1 of the position reference member202, the following formula is used to obtain a correction value:

Correction value=positional coordinate of the n-th sensor chip 210 (p-thpixel) in the sub-scanning direction+total inclination of the reader201×(m−p)

where p indicates the number of pixels (“p” pixels) counted from theleading pixel in the specific sensor chip used for calculating thecorrection value.

Further, a case where two readers 201A and 201B are arranged side byside are described.

FIG. 11 is an illustration of a method of correcting inclination of tworeaders 201A and 201B according to an embodiment of the presentdisclosure.

As illustrated in FIG. 11, when two readers 201A and 201B are disposedside by side, the readers 201A and 201B are independent from each other.In this case, the readers 201A and 201B have different coordinates inthe sub-scanning direction and different inclination degrees withrespect to the position reference member 202.

When the readers 201A and 201B are disposed side by side, the correctionunit 114 calculates the inclination of each of the reader 201A and 201Bfrom the coordinates in the sub-scanning direction of the both ends ofthe readers 201A and 201B), so as to perform the correction operation.

The same applies to the case where three or more readers 201 arearranged side by side.

As to the readers 201A and 201B, the horizontal line X1 of the positionreference member 202 is not required to be read by each sensor chip 210at substantially the same pixel position. Instead, the horizontal lineX1 of the position reference member 202 can be read by each sensor chip210 by changing the pixel position for each sensor chip 210.

The position detection unit 115 detects the outer shape of the recordingmedium and the position of the image pattern on the recording mediumfrom the image read by the reader 201.

FIGS. 12A, 12B, and 12C are illustrations of a method of calculating theouter shape of the recording medium and the position of an image patternon the recording medium.

As illustrated in FIGS. 12A and 12B, an L-shaped image pattern “P” isformed at the four corners “O” of the recording medium such as a sheet(e.g., paper). The position detection unit 115 detects the sheet edgeand the beginning and end coordinates of the image pattern from theimage levels in the main scanning direction and the sub-scanningdirection. For example, when the outer shape of the recording medium isto be obtained, the position detection unit 115 detects the coordinatesof four positions in the main scanning direction and four positions inthe sub-scanning direction, and obtains the intersection points of thesepositions as the four corners “O” at the edges of the recording medium.

As illustrated in FIG. 12C, the position detection unit 115 determinesthe sub-scanning directional coordinate in the case of detecting themain scanning directional coordinate (main scanning directionalcoordinate in the case of detecting the sub-scanning directionalcoordinate) when determining the intersection points on the recordingmedium, as an ideal value for a sub-scanning directional position thatdepends on the read position of the recording medium.

It should be noted that the position detection unit 115 can directlycalculate the four corners “O” when the memory has sufficient capacityand data of all the pixels is extracted from the storage unit (memory)before the ends of the recording medium is calculated.

FIGS. 13A and 13B are illustrations of examples of images detected bythe reader 201. FIG. 13A is an illustration of a detected image when thereader 201 is disposed orthogonal to the direction of conveyance of therecording medium. FIG. 13B is an illustration of a detected image whenthe reader 201 is inclined with respect to the direction of conveyanceof the recording medium.

As illustrated in FIG. 13B, if the reading device 201 is inclined withrespect to the direction of conveyance of the recording medium, theimage detected by the reader 201 appears distorted by the amount ofinclination of the reader 201.

Therefore, in the present embodiment, the position detection unit 115refers to the position in the sub-scanning direction corrected by thecorrection unit 114, used to detect the position of the recordingmedium.

FIG. 14 is an example of an illustration of a table of the correctionvalue for an example case of FIG. 13B.

Next, the correction value processing executed by the printing system 1will be described.

FIG. 15 is a flowchart of the correction value processing. Asillustrated in FIG. 11, upon detecting a horizontal-line reading starttrigger, the horizontal line detection unit 112 starts reading thehorizontal line X1 of the position reference member 202 while moving theposition reference member 202 in the sub-scanning direction (step S1).

More specifically, the horizontal line detection unit 112 causes themotor control unit 111 to move the position reference member 202 in thesub-scanning direction. Further, the horizontal line detection unit 112reads the position reference member 202 moving in the sub-scanningdirection, using the reader 201 under the control of the reading controlunit 110.

When the reading operation performed by the reader 201 ends, the reader201 outputs a reading end trigger to the horizontal line detection unit112.

Upon receiving the reading end trigger, the horizontal line detectionunit 112 stops the position reference member 202 moving in thesub-scanning direction, so that the position reference member 202 is setin a standby state.

Further, upon receiving the reading end trigger, the horizontal linedetection unit 112 detects the coordinate in the sub-scanning directionof each sensor chip 210 of the reader 201 (step S2).

Next, the detection result storage unit 113 stores the coordinate ofeach sensor chip 210 of the reader 201 detected by the horizontal linedetection unit 112, in the storage unit (step S3).

Next, the correction unit 114 calculates a correction value of theinclination of the reader 201 (step S4).

With such a configuration according to the embodiment of the presentdisclosure, the displacement of the installation position of the reader201 can be accurately detected irrespective of the inclination of thereader 201 and the position of each sensor chip 210 of the reader 201.

In the present embodiment, a CIS, which is an equal magnificationoptical system, is applied as the reader 201. However, no limitation isintended thereby.

For example, the reader 201 may be a so-called reduced optical systemincluding a light source, a plurality of reflection members (mirrors),an imaging lens, and a linear image sensor. That is, the reader 201 maybe any device capable of detecting the position of a target to be read,and the use of such a device can improve an accuracy of detection ofpositions.

In the present embodiment, the total inclination of the reader 201 iscalculated from the coordinates in the sub-scanning direction obtainedby reading two horizontal lines X1 corresponding to the sensor chips 210at the end of the reader 201. However, no limitation is indicatedthereby.

Alternatively, the total inclination of the reading device 201 may becalculated from the coordinates in the sub scanning direction at whichthe horizontal lines X1 corresponding to all of the sensor chips 210have been read, so as to calculate correction values for all the pixels.In the above-described embodiments, the cases where the reading deviceand the image forming apparatus mounted with the reading device areapplied to a printing system including an electrophotographic printingapparatus are described. Alternatively, the reading device and the imageforming apparatus mounted with the reading device may be applied to aprinting system including an ink-jet printing apparatus.

In the above-described embodiments, the cases where the reading deviceand the image forming apparatus mounted with the reading device areapplied to a printing system including a printing apparatus such as acommercial printing machine (production printing machine) are described.Alternatively, the reading device and the image forming apparatusmounted with the reading device are applicable to any image formingapparatus such as a multifunction peripheral having at least two of acopy function, a printer function, a scanner function and a facsimilefunction, a copying machine, a printer, a scanner, and a facsimileapparatus.

Furthermore, in the above-described embodiments, the cases where thereading device is used to detect the positions in the field of formingan image are described. Alternatively, the reading device according tothe present disclosure may be applied to position detection applicationsin various fields such as inspection in the factory automation (FA)field.

Further, the reading device according to the embodiments of the presentdisclosure is applicable in a bill reading apparatus that determineswhether bills are printed in correct positions and shapes so as todiscriminate bills and prevent forgery.

Further, the reading device according to the embodiments of the presentdisclosure is applicable in a bill reading apparatus that determineswhether bills are printed in correct positions and shapes so as todiscriminate bills and prevent forgery.

Any one of the above-described operations may be performed in variousother ways, for example, in an order different from the one describedabove.

Each of the functions of the described embodiments may be implemented byone or more processing circuits or circuitry. Processing circuitryincludes a programmed processor, as a processor includes circuitry. Aprocessing circuit also includes devices such as an application specificintegrated circuit (ASIC), DSP (digital signal processor), FPGA (fieldprogrammable gate array) and conventional circuit components arranged toperform the recited functions.

Although the embodiments of the present disclosure have been describedabove, the present disclosure is not limited to the embodimentsdescribed above, but a variety of modifications can naturally be madewithin the scope of the present disclosure. Numerous additionalmodifications and variations are possible in light of the aboveteachings. It is therefore to be understood that within the scope of theappended claims, the embodiments may be practiced otherwise than asspecifically described herein. For example, elements and/or features ofdifferent illustrative embodiments may be combined with each otherand/or substituted for each other within the scope of this disclosureand appended claims.

What is claimed is:
 1. A reading device comprising: a position referencemember having a reference pattern having a line extending along a firstdirection of the position reference member, the position referencemember movable in a second direction orthogonal to the first direction;a reader including a plurality of sensor chips arranged along the firstdirection, each of the sensor chips having a length defined by aplurality of pixels; and circuitry configured to: detect the referencepattern of the position reference member using the reader; determinecoordinates of at least two sensor chips in the second direction, basedon the detected reference pattern of the position reference member; andcorrect a position of a reading target in the second direction based onthe coordinates determined for the at least two sensor chips of thereader in the second direction.
 2. The reading device according to claim1, wherein the position reference member is configured to move in thesecond direction, relative to the reader.
 3. The reading deviceaccording to claim 1, wherein the circuitry is configured to calculate acorrection value in the second direction at a pixel used for detectingthe position of the reading object.
 4. The reading device according toclaim 3, wherein the circuitry is configured to: obtain an inclinationof the reader based on the detected coordinates determined for the atleast two sensor chips in the second direction; and calculate thecorrection value based on the obtained inclination of the reader.
 5. Thereading device according to claim 1, wherein the reference patternincludes a vertical line extending along the second direction of theposition reference member.
 6. The reading device according to claim 5,wherein the reference pattern further includes a horizontal lineextending along the first direction, the horizontal line existing nextto the vertical line, and wherein the horizontal line is in contact withthe vertical line at an end of the horizontal line.
 7. An image formingapparatus comprising: the reading device according to claim 1; a printengine; and circuitry configured to: control a conveyance of a recordingmedium onto which an image is formed by the print engine; detect anouter shape of the recording medium and a position of an image patternon the recording medium by reading the image formed on the recordingmedium using the reading device; correct a position of a reading targetin the second direction based on the coordinates determined for the atleast two sensor chips of the reader in the second direction.
 8. Amethod of calculating a correction value using a position referencemember including a reference pattern having a line extending along afirst direction of the position reference member, the position referencemember movable in a second direction orthogonal to the first direction,and a reader including a plurality of sensor chips arranged along onedirection of the reader, the method comprising: detecting, using thereader, the reference pattern having the line extending along the firstdirection of the reference pattern member, the reference patterncorresponding to each of the plurality of sensor chips arranged alongthe one direction in the reader, and each of the sensor chips having alength defined by a plurality of pixels; determining coordinates of atleast two sensor chips in the second direction, among the plurality ofsensor chips, based on the detected reference pattern of the positionreference member; and correcting a position of a reading target in thesecond direction based on the coordinates determined for the at leasttwo sensor chips of the reader in the second direction.
 9. Anon-transitory recording medium storing a program for causing a computerto execute the method according to claim 8.